If you've got a trip west of London booked this winter, check your plans now. Great Western Railway is closing a key stretch of track around Dolphin Junction, between Slough and Langley, as part of a £27 million upgrade — and the knock-on effects hit London Paddington itself.

The first closure lands on the weekend of 28 and 29 November 2026. During those two days, GWR will run special diversionary trains from London Euston instead of Paddington, with hourly services to Bristol Temple Meads, Swansea and Carmarthen. The catch: those trains can't stop anywhere between Euston and Swindon, so if you're heading to Oxford or Didcot Parkway you'll need a different plan.

Reading travellers get a workaround too. GWR is laying on extra non-stop trains between Reading and Guildford — around 30 minutes — where you can change for Waterloo services into London. Slow, but it works.

The Night Riviera sleeper is affected in an odd way: it still leaves Paddington as normal on Friday 27 November, but arrives into Euston from Penzance on Saturday morning, then departs from Euston on Sunday evening and returns to Paddington Monday morning. Book a hotel near the right station.

Airport transfers take a hit as well. Heathrow Express and Elizabeth line services won't run to or from Heathrow via Paddington that weekend — find an alternative route into central London, like the Piccadilly line, a coach or a taxi. On the Underground, only the Bakerloo line will serve Paddington over the two days, and the Elizabeth line runs a reduced Reading–Maidenhead service with nothing through Paddington to Abbey Wood or Shenfield.

It doesn't stop there. The Dolphin Junction works also affect 10 days over the festive period, with the railway closed between Paddington and Slough from 27 December 2026 to 3 January 2027, on top of the usual 25 and 26 December shutdown. GWR hasn't yet confirmed replacement arrangements for that block, so if your trip spans Christmas or New Year, keep an eye on announcements. The whole project is due to finish in January 2027.

The practical upshot: if you're travelling west on those dates, build in extra time and check whether you should book to Euston instead of Paddington. Anyone with an onward connection — a flight from Heathrow, a Saturday event in Oxford — should look at the diversions before travel day rather than discovering them at the barrier.